Add new-instance-open-target.window setting

This adds the ability to open new tabs in the last-focused window
instead, which fixes #1801.

Right now the only other option is probably not that useful for human
users but it's required to make tests behave deterministically and
consistently. (But with #881 on the roadmap, I would implement this as
another choice)

To this end, also make the test framework set this option to preserve
the invariant against which existing tests are written: that spawning a
new window would effectively also focus it.

qutebrowser/config/configdata.py

@@ -227,6 +227,16 @@ def data(readonly=False):
              "How to open links in an existing instance if a new one is "
              "launched."),
 
+            ('new-instance-open-target.window',
+             SettingValue(typ.String(
+                 valid_values=typ.ValidValues(
+                     ('last-opened', "Open new tabs in the last"
+                     "opened window."),
+                     ('last-focused', "Open new tabs in the most"
+                     "recently focused window.")
+                 )), 'last-focused'),
+             "Which window to choose when opening links as new tabs."),
+
             ('log-javascript-console',
              SettingValue(typ.String(
                  valid_values=typ.ValidValues(

qutebrowser/mainwindow/mainwindow.py

@@ -69,6 +69,10 @@ def get_window(via_ipc, force_window=False, force_tab=False,
         window_to_raise = window
     else:
         try:
+            win_mode = config.get('general', 'new-instance-open-target.window')
+            if win_mode == 'last-focused':
+                window = objreg.last_focused_window()
+            elif win_mode == 'last-opened':
                 window = objreg.last_window()
         except objreg.NoWindow:
             # There is no window left, so we open a new one

qutebrowser/utils/objreg.py

@@ -178,10 +178,7 @@ def _get_window_registry(window):
             app = get('app')
             win = app.activeWindow()
         elif window == 'last-focused':
-            try:
-                win = get('last-focused-main-window')
-            except KeyError:
-                win = last_window()
+            win = last_focused_window()
         else:
             win = window_registry[window]
     except (KeyError, NoWindow):
@@ -276,6 +273,14 @@ def dump_objects():
     return lines
 
 
+def last_focused_window():
+    """Get the last focused window, or the last window if none."""
+    try:
+        return get('last-focused-main-window')
+    except KeyError:
+        return last_window()
+
+
 def last_window():
     """Get the last opened window object."""
     if not window_registry:

tests/end2end/fixtures/quteprocess.py

@@ -330,6 +330,7 @@ class QuteProc(testprocess.Process):
         settings = [
             ('ui', 'message-timeout', '0'),
             ('general', 'auto-save-interval', '0'),
+            ('general', 'new-instance-open-target.window', 'last-opened')
         ]
         if not self._webengine:
             settings.append(('network', 'ssl-strict', 'false'))